Durvillaea antarctica

Durvillaea antarctica
Durvillaea poha (recently split as a new species from D. antarctica) stipes on Second Bay, Otago, New Zealand
Scientific classification
(unranked):	SAR
Phylum:	Heterokontophyta
Class:	Phaeophyceae
Order:	Fucales
Family:	Durvillaeaceae
Genus:	Durvillaea
Species:	antarctica
Binomial name
Durvillaea antarctica (Chamisso) Hariot

Durvillaea antarctica, commonly known as cochayuyo, is a large, robust bull kelp species and the dominant seaweed in southern New Zealand and Chile. D. antarctica has a circumpolar distribution between the latitudes of 29°S (in Chile) and 55°S (on Macquarie Island).^[1] It is found on exposed shores, especially in the northern parts of its range, and attaches itself with a strong holdfast. D. antarctica, an alga, does not have air bladders, but floats due to a unique honeycomb structure within the alga's blades, which also helps the kelp avoid being damaged by the strong waves.

Morphology

This cross-section and cut-away view of dried blades shows the honeycomb structure within

The blades of Durvillaea antarctica are green to golden brown with a leathery texture. The honeycomb structure of the blade gives strength and buoyancy.^[2] This novel structure is thought to be responsible for the wide distribution of this genus, as the kelp is able to float when its holdfast fails. It can colonise other coastlines in this manner, and has been shown to carry communities of invertebrates across vast ocean distances from one shore to another.^[3] It is thought that this 'rafting' with Durvillaea antarctica and other floating seaweeds allowed a wide range of species to recolonise sub-Antarctic shores scoured clean by ice during the last Ice Age.^[4]

The holdfast of D. antarctica is large and is very difficult to remove. D. antarctica has to resist forces equivalent to 1100 km/h on land.^[5] The holdfast failing is usually the result of worms and molluscs which feed on the tissue because of the sheltered habitat it creates.^[6] It is also common for its host rock to be broken off without the holdfast losing its grip, with this contributing significantly to erosion in some areas.^[1] Recruitment rates of this species is very low, therefore the ecological impact of harvesting this species is too great.^[6]

Durvillea antarctica. Washed up on Sandfly Bay, Otago, New Zealand

Life cycle

Durvillaea antarctica reproduces sexually by producing egg and sperm that are released into the water. Eggs and sperm are produced on specific sites of the frond. A large individual can produce 100 million eggs in twelve hours.^[6] The season when reproduction occurs varies with location, but is generally during winter months.

Dried D. antarctica in a Chilean market

Chilean culture

Use in cuisine

In Chilean Cuisine, the Durvillaea antarctica (Quechua: cochayuyo : Cocha: Lake, and yuyo: weed) stem and holdfast, known as hulte is used for different recipes, like salads and stews.

Expression

The expression remojar el cochayuyo (lit. to soak the cochayuyo) is used in Chilean Spanish to refer to sexual intercourse.^[7] The expression derives from the fact that this algae, that is harvested along Chile's coast, is preserved by being sun-dried and to prepare it then in a dish it needs to be softened up by being soaked in water.

Taxonomy

The species was first described in 1822,^[8] as Fucus antarcticus, and revised in 1892 as Durvillaea antarctica.^[9] The genus name Durvillaea was given in memory of the French explorer Jules Dumont d'Urville, while the Latin derived epithet refers to antarctic.^[10] Recently, taxonomic revision led to the recognition of a new species, Durvillaea poha, within what was previously considered Durvillaea antarctica. Durvillaea poha is the only other species in the genus to share the honeycombed structure and buoyancy of D. antarctica. D. poha occurs only in southern New Zealand and on some New Zealand islands (including the Auckland and Snares Islands), whereas D. antarctica has a wider distribution, and is found around New Zealand, Chile and the sub-Antarctic islands. In southern New Zealand, D. poha and D. antarctica can be found growing together, although D. poha normally grows higher up or further back on the rock platforms, or in more sheltered bays, where wave force is weaker.^[11] D. poha generally has wider fronds than D. antarctica, and can appear more 'orange' across the frond area.

References

1. Smith, J.M.B. and Bayliss-Smith, T.P. (1998). Kelp-plucking: coastal erosion facilitated by bull-kelp Durvillaea antarctica at subantarctic Macquarie Island, Antarctic Science 10 (4), 431–438. doi:10.1017/S0954102098000522.
2. Maggy Wassilieff. Seaweed - Bull kelp’s honeycombed structure, Te Ara - the Encyclopedia of New Zealand, Ministry of Culture and Heritage. Updated 2 March 2009. Retrieved 9 March 2010.
3. Fraser CI, Nikula R & Waters JM (2011) Oceanic rafting of a coastal community. Proceedings of the Royal Society, B, 278:649-655.
4. Fraser CI, Nikula R, Spencer HG & Waters JM (2009) Kelp genes reveal effects of subantarctic sea ice during the Last Glacial Maximum. Proceedings of the National Academy of Sciences, USA, 106:3249-3253.
5. Hurd, C (2003). The Living Reef. Nelson, New Zealand: Craig Potton Publishing.
6. Bradstock, M (1989). Between the Tides. New Zealand: David Bateman Limited.
7. La Ficha Pop, La Cuarta, 31 October 2006.
8. Choris, L. (1822). Voyage pittoresque autour du monde. Part I. pp. vi + 17, 12 plates. Paris
9. Hariot, P. (1892). Complément à la flore algologique de la Terre de Feu. Notarisia 7: 1427-1435.
10. Guiry, M.D.; Guiry, G.M. (2008). "'Durvillaea antarctica'". AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.
11. Fraser CI, Spencer HG & Waters JM (2012) Durvillaea poha sp. nov. (Fucales, Phaeophyceae): a buoyant southern bull-kelp species endemic to New Zealand. Phycologia, 51:151–156.

External links

AlgaeBase: Durvillaea antarctica AlgaeBase: Durvillaea poha